What was found
EN ROUTE RIGHT AC PACK MAINTAINED 13 PSI, AC PRESSURIZATION CONTROLLER WENT TO STBY/LOCKOUT AT TOP OF DESCENT, CABIN PRESSURE CONTROLLER FAILED, PERFORMED EMERGENCY DESCENT. PERFORMED BITE CHECK ON BOTH CABIN PRESSURE CONTROLLERS. NO FAULTS FOUND. SWAPPED NR 1 CONTROLLER WITH NR 2 FOR TROUBLESHOOTING. REPLACED BOTH LEFT AND RIGHT WATER SEPARATOR COALESCER BAGS. PRESSURIZED BOTH PACKS. NO LEAKS NOTED. SYSTEM OPS CHECKED OK IAW DC9 AMM 21.00.00.5. MANUAL OPERATION OF OUTFLOW VALVE CHECKED OK.